The present invention is in the field of network communications, including Data Network Telephony (DNT), such as Internet Protocol Network Telephony (IPNT) and pertains more particularly to methods and apparatus for enhancing DNT in narrow bandwidth wireless links.
The art of telephony communication has grown in proportion with improved telephony infrastructure, equipment, and methods of practice. Conventionally and historically telephone communication has been practiced by use of networks that provide dedicated connections and guaranteed bandwidth, such as in Publicly Switched Telephony Networks (PSTN). In such networks a call placed from a telephone connected to a local service is switched over dedicated channels to a destination, and as long as the connection is maintained, the dedicated path, having a dedicated bandwidth, is also maintained. Such networks may be termed Connection Oriented/Switched Telephony (COST) networks, and this term is used in this specification.
More recently, with the development of extensive data networks, of which the well-known Internet is a prime example, a newer type of telephony communication has been introduced. This form of telephony is termed herein Data Network Telephony (DNT), and, in the context of the Internet data network Internet Protocol Network Telephony (IPNT). Data networks typically link computers over one or more sub-nets, which may include local area networks (LAN), wide area networks (WAN) such as the Internet, company Intranets, and combinations of these and other data networks.
In DNT, such as IPNT, dedicated connections are not provided except in rare and special instances. Instead, digital audio data is prepared in standardized audio packets complete with header information and the like. The packets are prepared in near real-time and broadcast over the data network(s) connecting involved computers adapted for DNT applications. The header for each packet includes a destination for the packet.
Data Network Telephony, such as IPNT is well-known in the art, and wireless data transmission is also quite well-known in many applications. Internet service providers, for example, are recently providing high data-rate wireless Internet access by satellite systems, and, where bandwidth is not substantially restricted at the receiver""s end, such systems have proven successful for WEB page delivery and the like. Such systems have not proved to be friendly for DNT applications, and there are a number of reasons, which apply to these kinds of systems and to other kinds of wireless systems of more limited bandwidth even more so.
The problems for Data Network Telephony in wireless systems are related to the real-time nature of telephony data and the typically limited bandwidth available in such systems. In relatively high-bandwidth systems having a relatively large number of users the distribution probabilities provide a situation where it is uncommon for several or many users to demand unusual bandwidth at the same time. The phenomenon is known in the art as averaging. Even with known high-use times, it can be expected that distribution will be such that bandwidth will be adequate. In most wireless systems however, bandwidth is more precious, and averaging is hence not as helpful.
A contributing problem is in the nature of real-time audio data as opposed to data transmitting stored documents and the like, which may be called data-data as opposed to voice-data. Data-data is prepared in packets for transmission from stored data of known capacity. The number of data packets needed to transmit a stored document, whether text, graphic, audio, or other, is a known quantity. Moreover, there is no fundamental loss if such data becomes delayed in transit. Once it arrives at a destination, the document may be reproduced.
Voice-data packets for real-time conversations are different. The packets for voice-data have to be prepared and transmitted in essentially real time in both directions or a meaningful conversation cannot be held. Moreover, the magnitude of packaged voice-data for a conversation will be inflated by acoustical background noise, which under some conditions can double or triple or even further multiply the amount of data having to be sent, imposing severe demand on available bandwidth.
The inventor has carefully considered the possibilities of a number of types of potential DNT applications, and has determined that it is desirable to provide DNT in wireless systems of many sorts to take advantage of some of the inherent advantages of DNT over dedicated connection-type telephony systems, and to provide DNT capability in systems that also are capable of data transfer of the data-data type described above, such as of stored digital documents and entities. A novel system in this patent application is proposed, for example, using relatively small, battery-powered, hand-held computer communicators with DNT capability to be carried by users within range of multiple Network Interface Adapters (satellite transceivers). In a preferred embodiment wireless communication is provided by RF signaling. The invention, however, is not limited to RF, and could be implemented in an Infra system or any other system providing wireless communication.
In such a system the Network Interface Adapters may be coupled, for example, to a Local Area Network. Such a system would be quite useful on a company premises for workers to keep in touch, hold phone conversations, share documents locally (Campus Intranet), and communicate with the Internet and other connected computers as well (Inter Campus Intranets or Extranets). Many variations of such systems are possible, but present technology does not render such systems really practical. Methods and apparatus according to various embodiments and aspects of the present invention, taught in enabling detail below, provide substantial improvements rendering such voice/data systems on narrow bandwidth links quite feasible and useful.
In a preferred embodiment of the invention a data network telephony (DNT) system is provided, comprising a base station connected to a DNT-capable data network and to a wireless transceiver and adapted to operate the transceiver by a two-way, narrow-band, multiple-channel, real-time duplex radio protocol; and a plurality of portable computer-enhanced communicator units, including microphone and speaker apparatus, each adapted to communicate with the base station by the two-way real-time radio protocol and to process DNT calls. The base station is further adapted to process DNT calls on the DNT-capable data network and to broadcast and receive the DNT calls to and from the plurality of communicator units via the transceiver as DNT data packets. In one embodiment DNT-capable data network is a local area network (LAN).
In preferred embodiments one or more of the communicator units is equipped with Digital Signal Processors (DSPs) adapted for recognizing human speech, and audio data for DNT calls is processed by the DSPs, allowing substantially only human speech to be prepared as DNT packets for transmission.
In another aspect, related to noise reduction one or more of the communicator units is equipped with noise cancellation microphone and speaker apparatus adapted for creating a noise reduction zone in the region of a principle speech input microphone. A method is provided for a system providing wireless communication between a portable communication unit and a base station over a dedicated channel, wherein the portable device is adapted for Data Network Telephony, a method for minimizing data traffic in the channel, comprising steps of (a) accepting speech at a microphone at the portable communication unit; (b) processing the speech by a digital signal processing (DSP) system adapted to distinguish between human speech and background noise; and (c) preparing and transmitting data packets from substantially only the human speech. In this method in some embodiments the DSP function is provided by a specific chip or chip set coupled to an internal bus of the portable device. In others the DSP function is provided by a CPU of the portable communication unit.
In yet another aspect of the invention, in a wireless communication system having a base station connected by a hard-wired link to a transmitter/receiver (transceiver), wherein a gross wireless bandwidth is allocated by channels for individual users, a method is provided for ensuring sharing of the bandwidth among the users, comprising steps of (a) mirroring the channel assignments for wireless communication to the users in the hard-wired link, creating thereby virtual channels in the hard-wired link; and (b) transmitting data meant for a specific channel to the transceiver for wireless transmission according to the virtual channels imposed on the hard-wired link.
The unique nature of the wireless communication of the present invention provides the advantages of real-time data-network packet telephony in a very narrow-band system, extending the technology of such telephony into the realm of hand-held, portable communicators.